The aerodynamic air cleaner is a newly developed vane-induced uniflow cyclone to achieve high particle separation efficiency at low pressure-drop. It comprises of a vanes region, a straight region, a converging region, and a dust bunker. The particle separation mechanisms of the aerodynamic air cleaner were studied in this research by using theoretical analyses, experimental investigations and computational fluid dynamics simulations. This technology was also applied in cooling air cleaning for the radiator of a combine harvester.

Particle separation efficiency due to converging effect of an aerodynamic air cleaner was first analyzed under laminar and complete mixing conditions. Instead of one curve, this model gave an efficiency range in which the actual particle separation efficiency was expected to fall. The analysis also showed that the particle separation efficiency increased with the inlet air Reynolds number and the geometry factor and the particle density and diameter.

Particle separation mechanisms were also experimentally investigated using a laboratory prototype. The efficiencies of this prototype were measured under three inlet air Reynolds numbers - Re =9993, 17765, and 25581. The experiments were compared with the theoretical analyses and the Crawford model developed in 1976. It was found that the new model agreed with the experiments well, while the Crawford model under-estimated the particle separation efficiency. Nevertheless, the measured efficiencies for smaller particles were always lower than the predictions using the models. It was speculated that the separated particles reentered the air stream from the bunker. The smaller the particle, the higher the reentrainment effect was.

To verify the above speculation, the airflow pattern inside the identical prototype was characterized using a three-dimensional hotwire anemometer. It showed that the velocity variation within the straight region was much lower than in the dust bunker. Computational fluid dynamics (CFD) simulations using standard k-ɛ models also showed that the airflow turbulence inside the straight region was low. While the airflow inside the bunker was found highly turbulent and circulating. It confirmed that the reentrainment of particles from the bunker contributed to the lower separation efficiencies for smaller particles. In addition, the CFD simulations showed significant bouncing effects for large particles.

This aerodynamic air cleaning technology was applied for cooling air cleaning for the radiator of a combine. The major findings in the mechanism studies were employed to guide the prototype designs. Three prototypes were developed and evaluated in the laboratory and/or field. The pressure drops of these prototypes were less than 250 Pa, and the overall efficiency was in the range of 70-80%. Laboratory test results also showed that the efficiencies of the prototype with bunker aspirations were much higher than those without. It further confirmed that bunker design was critical for the performance of an aerodynamic air cleaner.

In summary, both mechanism studies and applications showed that it was necessary to study the effect of bunker design on the performance of an aerodynamic air cleaner. A properly designed bunker was expected to significantly increase the particle collection efficiency. Systematic studies on the bunker geometry, shape, material, and aspiration ratio were recommended. These studies could be conducted by comparing different physical models with the assistance of CFD simulations. In CFD simulations, user defined functions were strongly recommended for calculating the particle separation efficiency.